By making reference to various documents, such as U.S. Pat. No. 4,955,634 A, <Automobile Technology>, <Automobile Construction> and <Explanation of Merits and Demerits Regarding Various Forms of Suspension> (taken from www.liuzhou.bitauto.com dated Aug. 16, 2008) and comparing with the traditional technology, an existing vehicle suspension system is generally classified into dependent and independent suspension systems, and is equipped with an anti-skew bar apparatus to reduce vehicle skew when cornering.
As shown in FIG. 1, a dependent suspension system has a structure characterized in that: wheels at two sides are connected by one-piece frame, and the wheels together with the frame suspend underneath the car body through a resilient suspension system. The dependent suspension system has various advantages, such as simple structure, low cost, high strength and easy maintenance. However, both the comfort and stability of driving of the dependent suspension system are poor. When a wheel at one side hops, a wheel at the other side may also hop and the wheels skew, which may reduce the contact area with the road, aggravate tire wear, and decrease tire adhesion on the ground. Moreover, the dependent suspension system is not suitable for front suspension.
As shown in FIGS. 2 and 3, in an independent suspension system, wheels on each side are independently suspended underneath the vehicle frame or car body through a resilient suspension system. The independent suspension system has various advantages, such as light weight, reduced impact to the car body, increased adhesion of the wheels to the road. By using the independent suspension system, a soft spring with a low stiffness coefficient can be adopted to improve the comfort of automobile. The position of the engine can be lowered in order to lower the center of gravity of the automobile, so as to improve the vehicle's driving stability. Each of the left and right wheels hop independently and there is no interference therebetween, thus the inclination and shake of the car body can be reduced. However, the independent suspension system may have a complicated structure, high cost, and inconvenience on maintenance.
As described above, due to the inherent structural limit of the existing dependent and independent suspension systems, the wheels cannot keep perpendicular to the road surface, and wheel track, wheelbase and positioning parameters cannot keep unchanged during the movement of the vehicle. Since all the existing suspension solutions are based on axial movement, even if the most complicated suspension can only make variations of wheel track, wheelbase and positioning parameters of front wheels within acceptable ranges. That is, compromise may be made among various parameters that restraint and contradict with each other, and the perfect performance for suspension can't be achieved. It can be seen that all the existing suspension solutions are based on a way of rotating around an axle, and an anti-skew bar may connect wheels at two sides for sacrificing the performance of independent suspension in exchange of a limited anti-skew function. A perfect suspending apparatus can't be produced to approach an ideal driving, stability, comfort and safety of the vehicle if the above mentioned way is not abandoned.